1) Become very thin 2) Cause to grow thin or weak 3) Debilitate 4) Decline to skin and bones 5) Drain 6) Enfeeble 7) Get too thin 8) Grossly underfeed 9) Macerate 10) Make abnormally lean 11) Make abnormally thin 12) Make feeble 13) Make gaunt 14) Make thin 15) Make thinner 16) Make unhealthily thin 1) Waste 
• (v. t.) To cause to waste away in flesh and become very lean; as, his sickness emaciated him. • (v. i.) To lose flesh gradually and become very lean; to waste away in flesh. • (a.) Emaciated.
E·ma'ci·ate intransitive verb [ imperfect & past participle Emaciated ; present participle & verbal noun Emaciating .] [ Latin emaciatus , past participle of emaciare to make lean; e + maciare to make lean ...
make thin and weak 
[v] - grow weak and thin or waste away physically
verb grow weak and thin or waste away physically; `She emaciated during the chemotherapy`
to make abnormally lean or thin by a gradual wasting away of flesh.